It is often necessary with agricultural vehicles to enlarge the supporting surface of the wheel for tilling the fields in order to keep the soil pressure at a minimum. This is achieved by mounting an auxiliary wheel on each of the wheels of the vehicle. The mounting and the removal of these auxiliary wheels should be achieved quickly and without great effort, since driving on roads with the mounted additional tires is often not allowed owing to the over-dimensional width. Therefore it should also be possible to mount and remove the auxiliary wheels in the field, for example.
Also in the case of other vehicles, for example construction machines, which have to be driven in open country, it can be advantageous if the supporting surface of the wheels can be enlarged, for example to prevent sinking in a soft subsoil. The same device can be used here as for the aforementioned agricultural vehicle.
Devices of this kind are known. In these devices ring bolts are installed on the wheel of the vehicle, preferably on the wheel bowl, distributed about the circumference. Engaging in the ring of each of these bolts is a hook, which is formed at one end of the connecting rod. The other end of the connecting rod engages in a hook which can be tensioned, which can be hung on the rim of the auxiliary wheel, and which can be firmly tensioned via a tension lever. The auxiliary wheel is hereby tensioned against a distance sleeve, mounted between the two wheels, and is tensioned with this sleeve on the wheel of the vehicle. The adjustment of the length of the tensioning means takes place by turning the connecting rod, which is screwed into the tensioning element via a threading. A device of this kind is described, for example, in EP-A-0 084 979.
A similar installation is described in U.S. Pat. No. 3,836,202. Here, too, a connecting rod is used whose one end is shaped as a hook and can be hung in a ring-shaped screw fastened to the wheel. The other end of the connecting rod is provided with a threading on which a tensioning nut is screwed, which is supported on a claw which can be hung in the auxiliary wheel. To tension the tensioning means, the tensioning nut must be tightened by means of screw spanner.
The driving forces of the wheel must also be transmitted to the auxiliary wheel through this prior art device tensioning means, disposed distributed about the circumference. Consequently the force to be absorbed by the tensioning means is relatively great. This means that the hook, which can be hung in the ring bolt, must be dimensioned big, or the number of tensioning means provided for attaching the auxiliary wheel must be increased. Nevertheless there is the risk that the hook of an individual tensioning means might bend or even break.
The object of the present invention therefore consists in improving the transmission of forces from connecting rod to anchor part such that the corresponding elements can be dimensioned small so that material can be saved, or in the case of the same dimensioning, the number of tensioning means per wheel can be reduced so that costs can be lowered and the mounting and removal of the auxiliary wheel can be achieved with less effort.